The present invention pertains to the field of medical devices. More particularly, the present invention relates to image processing in endoscopic camera systems.
Endoscopy is a medical field that allows the acquisition of high-quality video A images of internal features of a human body, without the need for invasive surgery. A basic tool of endoscopy is an endoscopic camera system, which includes an endoscope (xe2x80x9cscopexe2x80x9d) that is inserted into the body of a patient. Some endoscopic procedures involve the use of a flexible scope, as in the field of gastroenterology, for example. Other procedures, such as arthroscopy or laparoscopy, involve the use of a rigid scope. The scope is normally connected to a camera head that includes electronics for acquiring video image data through the scope.
The connected scope and camera head may be held and manipulated during endoscopic surgery by a human surgical assistant or by a holding tool, such as a robotic positioning system. The scope has optical properties that allow it to introduce light into the body of the patient and to transmit light from the body cavity to the camera head. A high intensity light source may be coupled to the scope by a fiber optic cable to introduce light into the body. The camera head is coupled through a flexible transmission line to a camera control unit, which is often mounted on a mobile cart. The control unit processes video data provided by the camera head to generate images, which are displayed on a video monitor. The control unit may also be coupled to various peripheral devices, such as a printer and a videocassette recorder (VCR).
During endoscopic surgery, the person who is holding the scope may not be able to hold the scope perfectly still, especially when fatigue sets in. This may cause the displayed video image to fall out of focus. Hence, the video image normally must be refocused frequently during surgery. Also, many endoscopic system installations make use of several different types of scopes, old and new, from various companies. The combinations of these systems cannot necessarily provide optimal depth of focus for all surgeries. In some endoscopic camera systems, focusing is done by manually adjusting to the optics between the scope and the camera head. This approach has disadvantages, however. For example, manual focusing consumes valuable time during surgery. Further, the refocusing process may involve several trial-and-error steps as the scope holder makes corrections in response to verbal feedback from the surgeon.
Some camera systems provide the capability to automatically focus the image. However, such systems still rely upon mechanical focusing, that is, adjusting the physical configuration of the optics within the scope and/or its connection to the camera head, although the adjustment is done under electric control. These systems take a measurable amount of time to adjust when the image becomes unfocused thus introducing a focusing lag. Because of this focusing lag, the adjustment is prone to a problem known as xe2x80x9covershootxe2x80x9d. Overshoot occurs when, during the time that the system is refocusing, the camera system has already fallen out of focus at the new position that the camera is attempting to adjust to. So, by the time that the system has moved to the new position, the system has to immediately begin to correct the focus, because the image would not be focused at this new position. To the surgeon, the image simply seems to continually move in and out of focus. Therefore, even these systems consume precious time to adjust and are subject to a certain amount of trial-and-error in focusing.
Another problem with some camera systems is that the focusing operation includes changing the size of the aperture in the camera. When the size of the aperture is decreased, the resolution of the image tends to be decreased. Also, decreasing the size of the aperture allows less light to go through the aperture. Less light going through the aperture causes the video image to become dimmer, making it harder to see detail in the image. Thus, a focusing mechanism is desired that keeps the image in focus without sacrificing brightness or the resolution of the video image.
Yet another problem with mechanically focusing endoscopic camera systems is the occurrence of failure. In general, moving parts are more likely to break down than electronic components. Because the mechanical systems must use moving parts in order to adjust the optical components, they are more likely to break down. This is especially true with endoscopic cameras and accessories that undergo harsh sterilization environments and rough handling. Such failures are expensive and can have serious consequences if they occur during surgery.
An endoscopic camera system includes the capability to receive image data from an endoscopic camera and to process the image data to generate images, including the capability to automatically and non-mechanically focus images. Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.